Devices within close proximity may wirelessly transfer energy for various reasons. For instance, a device may wirelessly charge another device's battery. Also, two devices may engage in near field communications (“NFC”).
NFC and wireless charging are emerging technologies that are integrated into mobile platforms such as tablets, smartphones, notebooks and other small computing devices (e.g., Ultrabook™ device—Ultrabook is a trademark of Intel Corporation in the U.S. and/or other countries). Both are forms of wireless energy transfer, one for the purpose of communications, and the other for the purpose of charging a rechargeable energy store such as a battery. Such wireless energy transfer may involve an electromagnetic coupling between proximate coils that may act as antennas. For example, a first device may have a transmitting coil and a second device may have a receiving coil. The coils are made of an electrically-conductive material. An electrical current flowing through the transmitting coil generates a magnetic field. In turn, the magnetic field may induce an electrical current in the receiving coil. The electrical current may be modulated, producing a modulated magnetic signal and thus transmitting information.
NFC is an emerging technology and desirable feature that is integrated into mobile platforms such as small computing devices, (e.g., clamshell, slider and convertible configured systems), tablets, smartphones and handhelds. They are expected to lead to new touch based communication usages. These usages can be broadly classified into: a) Device owner tapping two of her own devices together, e.g. to pay on a personal point-of-sale (POS) with a handheld or credit card; and b) peer to peer (P2P) tap, where two people each with their own device tap to enable pairing, transfer etc.
As touch screens and/or sensors take increasingly more real estate on a mobile device, NFC and/or wireless charging coils have been placed under touch sensor/touch screens. However due to the blockage of touch sensor and system power constraints, the user experience of reading a NFC-enabled device (e.g., a credit card) through the touch sensor/screen is not sufficiently satisfying. It is especially unsatisfying when cards or tags of different form factors (i.e., shapes) are presented at various orientations to the NFC coil underneath the touch sensor/screen.
The performance and effectiveness of NFC and wireless charging is very sensitive to size, relative location and orientation of the two coils involved. For instance, when a misalignment exists between transmitting and receiving coils, a smaller electrical current is induced in the receiving coil. As a result, a reduced energy transfer occurs. This may unfortunately reduce the efficacy of wireless charging and NFC applications.
Some conventional solutions to improving NFC performance involve adding an external amplifier between the NFC modules and coil to boost the signal. However, doing so consumes more power and sometimes causes co-existence problems with the touch sensor/screen. Other conventional solutions for both NFC and wireless charging involve providing switchable coils to create larger charging or card reading area. However, switching between multiple coils alone will cause a slow response to the user and thus produce an unsatisfying user experience.
Because NFC-enabled devices may be reconfigured during use into a variety of lid modes, a single NFC antenna is unable to provide adequate coverage for all modes. Therefore, there exists a need to provide improved NFC performance for an NFC-enabled device that may be reconfigured into more than one physical configuration.